Purge means for rectangular precipitator



May 19, 1959 P. HODSON 2,387,175

' PURGE MEANS FOR RECTANGULAR PRECIPITATOR -Filed Dec. 6. 1956 {I l l l .6 l

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HWENTOQ peter #00500 Patented May 19, 1959 PURGE MEANS FOR RECTANGULAR PRECIPITATOR Peter Hodson, Wellsville, N.Y., assignor to Apra PrecipiQ tator Corporation, New York, N.Y.,Ka corporation of Delaware Application December 6, 1956, Serial No. 626,715

6 Claims. (Cl. 183-7) The present invention relates to gas cleaningapparatus and more particularly to an arrangement for removing dust particles from the collecting surfaces of an electrostatic precipitator on which they have been deposited by a process of electrostatic precipitation.

In gas cleaning apparatus of the electrostatic type, dust laden gases are directed through a strong electric field between discharge electrodes and groundedcollector surfaces. As the dust particles entrain'edin the gas stream become electrically charged, they moveunder the influence of the strong electric field to the grounded collector surfaces upon which they are deposited.

In order that the dust collecting apparatus may be maintained at a high operating efficiency itis of primary importance that all electrodes and collecting surfaces be periodically subjected to a cleaning action to remove the deposited particles and thereby present a substantially clean surface to the incoming dust entrainedfluid. Since the operating efficiency of dust collectingapparatus is dependent to a large extent upon the efficiency with which the deposited particles are removed from the collecting surface of the precipitator, it is an object of this invention to provide an arrangement for efficientlyremoving the deposited particles from the collecting surfaces thereof thereby preventing them from reentrainment in the clean gas stream issuing from theprecipitator. p t

In modern steam boiler installations of the larger sizes which utilize gas cleaning apparatus .of the general type herein disclosed, the dust collecting surface must necessarily be so extensive that it is not feasible to clean a. large portion of the surface with the purging technique usually employed since the demand for purging fluid would be far greater than the supply of fluid that can be made economically available. Therefore another object of this invention is to provide an arrangement which subjects only a portion of the entire dust collecting surface to a cleaning action at any particular instant whereby a minimum amount of purging fluid will be required to provide an eflicient purging action. a q

A further object of this invention is to provide a purg ing arrangement for gas cleaning apparatus which has a minimum of interference with normal operation of the apparatus. g g

A still further object of this inventiomis to provide a purging means so eflicient that it is not necessary to shut off power to the compartment being cleaned thereby achieving a substantial saving in cost of controls.

The invention will be best understood upon considera tion of the following detailed description of an illustrated embodiment thereof when read in conjunction with the accompanying drawing in which the single. figure shows a perspective view partially in section of an electrostatic according to this invention. I

In the drawing the numeral 10 designates the housing of an electrostatic precipitator having an inlet through which dust laden gases enter to pass upward throughcollecting compartments 18 to a duct 20 from which theclea'ned 2 gases are vented. The compartments 18 lie between a series .of transverse. division plates 22 which extend through thc housing in a. plane normal to the longitudinal partitions- 24. At the upper end of compartments 18 a series of converging extensions 19 thereto form continuationsfwho se end faces combine to form a perforate arcuate surface 26 whose ports discharge cleaned gases into outletvchamber 29. An imperforate sealing surface 27 continuing from the arcuate surface 26 forms therewith a completely cylindrical member enclosing chamber 29 which directs cleaned gases axially outward through outlet duct 20.

Radial support bearings 28 supported by the housing structure at axially remote ends thereof support trunnions 30 for rotation. about theirlongitudinal axis. A plurality of axially contiguous but circumferentially displaced branch ducts 36 depending from a cylindrical duct 34 are adapted to rotate therewith about the axis of the hearing supported trunnions. These branch ducts 36 are each provided at their distal ends with a sealing surface 35 arcuately formed to supplement the arcuate surface of the cylindrical member. .The end openings in the sealing surfaces 35 are adapted to sequentially register with the end. openings in the parallel banks of inclined compartments upon rotation of the central duct 34 and its appendingducts 36. A single branch duct 36 is provided foreach bank of compartments lying between longitudinal partitions 24 in such a manner that during construction the cleaning apparatus may be readily adapted to the cleaning of .additional banks of compartments by the provision of an additional branch duct 36 for each additional bank of compartments, the angular displacement of each duct being dependent upon the number of ducts. For example, a four bank precipitator as illustrated requires a cleaning arrangement having four branch ducts 36 each displaced degrees from one another. 'By the same" token a three bank precipitator would require three "branch ducts each displaced degrees while a precipitator having six banks of cleaning compartments would require a like number of branch ducts each displaced at an angle of 60 degrees from one another.

The .imperforate portion 27 of the cylindrical housing provides a. surface, which cooperates with the ends of the branch. ducts to seal them when they are in a confronting relationship, and only the particular branch duct in alignment with any of the several banks of compartments 18 will be open. to permit the flow of purging fluid therethrough. W As the duct 34 rotates about its axis and the branch ducts 36,are sequentially brought into alignment with adjacent collecting chambers 18, they in turn become active in thetransmiss ion of a purging fluid through the precipitator to a prescribed outlet. Sinceonly a single compartment 18 .is at any instant completely aligned with a branch duct 36 the quantity of purging fluid required to maintain a predetermined rate of flow through the compartments being purged is but a small portion of the capacity of theentire bank of collecting elements, and .continuous purging may be carried out without substantial reduction in theoverall cleaning capacity of the gas cleaning device.

Purging fluid for the cleaning device is drawn from the maingas flow by an induced draft fan (not illustrated) in outlet 39, the course of purgingfluid flow being from the precipitator inlet through a single compartment 1-8 thence through the branch duct 36 in agreement therewith to the precipitator w1th an mtegral cleaning device constructed central duct 34 and axially outward through ports 32 to outlet duct 39.

In operation the-central"duct 34 and its appending branch'ducts 36 arerotated slowly about their horizontal axis by an actuator such as a motor 42 acting through suit able reduction gearing '44. The device 44 may include mechanism for either continuous "or intermittent drive 'as may be deemed appropriate'for the conditions involved. As the central duct is rotated about its axisonly one complete branch duct 36 can 'at 'any time register with an extension 19 from compartments 18, all other branch ducts 36 being sealed against the'imperforatesurface of the cylindrical wall 27. As each branch duct is in turn moved into registry with succeeding extensions of compartments 18 a flow of'purgingfluid' is directed therethrough to the central duct 34 where it is then channeled through outlet ports 32'to exit duct 39. As the cylinder 34 is rotated the spaced branch "ducts 36 are sequentially moved past the collecting compartments into a confronting relationship with the imperforate arcuate surface 27 of the cylindrical housing where they are in turn sealed off as the next duct 36 is rotated into confronting relationship with the'extensions 19 of compartments 18.

By controlling the rotational speed of the central duct 34 and its appending branch ducts'36 "the purging operation may be readily varied to m'eet'changing conditions of dust loading and fluid fiow.

As outlined inthe objects of this invention, the purging action achieved by this arrangement is so e'fiicient, due largely to the relatively small surface area presenting itself for cleaning at anytime, that it is unnecessary to shut off power to the compartments'being purged. However, if it is deemed desirable to shut off the power this may readily be accomplished'by shutting it off only to that compartment which is in agreement with a duct 36. Since control of the power supply to each individual compartment would require extensive controls, economy in this respect may be 'achieved'by simultaneously controlling the power to each transverse bank of compartments adjacent the one being cleaned. In such instance it is necessary to temporarily block "off "such adjacent, 'compartments in order that the maingas .flow will .not v.eontinue to pass there'through.

While this invention .has been described with reference to the embodiment illustrated in :thedrawingit is evident that numerous changes might be made without departing from the spirit of the'invention and it is intended that all matter contained in the accompanying I drawings shall be interpreted as illustrative and not in a limiting sense.

What I claim is:

1. Gas cleaning apparatusincluding a, dust collecting section having a rectangular'hous'ing divided into banks of collecting compartments of an electrostatic precipitator by parallel division plates; an outlet, section superposed on the collecting section and divided into a series of converging compartments having ported 'ends'which terminate in a perforate arcuate, surface; an imperfora'te arcuate surface continuingfrom said perforate surface to form therewith a cylindrical duct member; purgingmeans for the removal of dust particles from the collecting section of said apparatus comprising in combination a discharge duct concentrically mounted within the cylindrical duct for rotation about) its longitudinal axis; means depending from the discharge duct adapted to direct the flow of purging fluid therethrough when in confronting relation with the perforate surface and to seal off theflow of purging fluid when in confronting relation with the imperforate surface thereof.

2. Gas cleaning apparatnsas defined, in claim 1 Wherein a plurality of branch ducts, extend from the discharge duct into confronting arrangement with the cylindrical housing member, saidbranch ducts being axially displaced tQ on ront at r lly adjacentnk f ol e P ments. i

3. Gas cleaning apparatuses defined in ctaim;2, wl1erein the axially spaced branch ducts are equally displaced circumferentially around the, arcuate-periphery ofifll'e discharge duct.

'4. Gas cleaning apparatus including a dust collecting *section having a'housing divided into banks of collecting compartments of an electrostatic precipitator by parallel division plates; an outlet section superposed on the collecting section and divided into a series of converging compartments whose ported ends terminate in an arcuate sealing surface; an imperforate arcuate surface "continuing from said perforate surface to form therewith a cylindrical housing member directing the flow of cleaned gas axially thereof; purging means for the removal of dust particles from the collecting compartments of said apparatus comprising in combination a discharge duct mounted centrally of said cylindrical housing .for rotation about its longitudinal axis; duct means depending from the discharge duct and terminating adjacent the inner surface of the cylindrical housing adapted to direct the flow of purging fluid from the collecting compartments to said discharge duct, said duct means rotatable with the discharge duct to provide an intermittent confronting relationship between the duct means and the perforate and imperforate surfaces of the cylindrical housing member.

5. Gas cleaning apparatus including a dust collecting section having a housing divided into banks of collecting compartments of an electrostatic precipitator by parallel division plates; an outlet section superposed on'the collecting section and divided into a series of converging compartments having ported ends terminating in an arcuate surface; an imperforate arcuate surface continuing from said perforate surface to form therewith 'a cylindrical housing member directing the flow of fluid therethrough; purging means for the removal of dust particlesfrom the collecting compartments of said apparatus comprising in combination a discharge ductrnounted concentrically within said cylindrical hou iug for rotation about its longitudinal axis; branch ducts depending from the discharge duct terminating adjacent the inner surface of the cylindrical housing adapted .to direct the flow of purging fluid from the several collecting compartments to the discharge duct; and means for continuously rotating the discharge duct about its longitudinal 6. Gas cleaning apparatus including a dust collection section having a housing divided into banks of collect ing compartments of an electrostatic precipitator by transverse and longitudinal banks of parallel division plates; 21 fluid inlet 'to the lower portion of said housing and'an outlet .scction superposed thereon to provide for the flow of fluid therethrough, said outlet section being divided into a series of converging compartments superposed on the collecting compartments and having ported ends which terminate in an arcuate surface; an imperforate arcuate surface continuing from said perforate surface to form therewith a cylindrical housing directing the flow of fluid therethrough; purging means for the removal of dust particles from the walls of the collecting compartments comprising in combination a discharge duct mounted within said cylindrical housing for rotation about its longitudinal axis; duct means depending from the discharge duct adapted to direct the flow of fluid from the collecting compartments to the discharge duct; and means for intermittently rotating the discharge duct about its longitudinal axis whereby adjacent banks of cleaning compartments are intermittently brought into confronting relationship with the d'uct'means.

References Cited in the file of this patent UNITED STATES PATENTS 2569;649- Abrams Feb. 20, 1945 2,391,534 Yerrick et a1. Dec. 25, 1945 2;'731,,l0 7 Hersey i.. Jan. 17, 1956 I FOREIGN PATENTS 5 610,391 Germany Mar. 9, 1935 

